Gas turbine plant, including multiple fluid operated motors with treatment between stages



Aug. 26, 1952 WELSH 2,608,055

GAS TURBINE'PLANT, INCLUDING MULTIPLE FLUID OPERATED MOTORS WITH TREATMENT BETWEEN STAGES Filed April 8,- 1949 SEPARATOR I VALVE CHAMBER 9 V nHHl WHT M v 322m M HEAT: zxcrmueen FIG. 2.

59' 5 J SEPARATING F 7Q VALVE7 cur-mesa 6. A I I NH g LOO A .COMPRESSOR HPTURBINE L'RTURBNE V llllll V W I com5usnoN I [0 mg L g CHAMBER HEAT EXCHANEER FIG. 2.

mvEmom ROBERT J. WELSH Patented Aug. 26, 1952 PLE FLUID OPERATED MOTORS WITH TREATMENT BETWEEN STAGES Robert James Welsh, Rugby, England, assignor to The English Electric Company Limited, London, England, a British company Application April 18, 1949, Serial No. 88,140 In Great Britain April 29, 1948 2 Claims.

This invention relates to constant pressure gas turbine .plant. It is concerned with the utilization of cheaper fuels than distillate oils or gas, such as relatively heavy fuel oil like that normally employed for burning under boilers, as-the fuel in such turbines.

Attempts hitherto made to use such fuel oil in gas turbines encountered, as one of the chief difficulties, that one or more of the metallic salts or other impurities in the oil tend to form compounds which appear in the burnt gases as vapours having dew points within the range of temperature through which the gas passes during its expansion in the turbine. The turbine blades in that region of the turbine in which the dew point of a fuel impurity (or of some compound containing the impurity, for example an oxide of the impurity) is substantially the ruling temperature, tends to become fouled with a deposit of the impurity or of its com und.

These deposits may in themselves adversely affect the operation of the turbine after a comparatively short time, but this detrimental efiect may be considerably increased in that these deposits are of a stickynature and. act as a trap for solid ash particles which may otherwise have passed harmlessly through the turbine. It thus occurs that under some load conditions a considerable amount of ash tends to be deposited on some adjacent rows of turbine blades while the remainder of the blades remains comparatively free from fouling. The building up of ash deposits on the turbine blades may cause a marked falling off in efficiency and general performance of the plant and thus causes serious inconvenience. It is an object of the present invention to overcome, or at least to reduce the magnitude of, these difiiculties.

According to a main feature of the invention a constant pressure gas turbine plant is provided with means for removing undesirable combustion products which appear only as gases, vapours or smokes in the combustion chamber but as a result of the cooling of the gas during expansion through the turbine would appear as undesirable liquids or solids in the turbine, said means comprising a separating chamber arranged between two stages of the gas turbine in series flow arrangement with one another, the temperature of the gases leaving the stage preceding the said separating chamber being at or slightly above the dew point of said undesirable combustion products, and cooling means for controlling the outlet temperature from the said separating chamber to a value slightly below the said dew point. The said stages of the gasturbine may be formed as stages of a single unit or as two consecutive separate units.

Preferably such a plant is so operated that the combustion gases are cooled in said separating chamber from a temperature just above (of the order of 10 C. above as may be appropriate) the dew point of any vapours present in them to a temperature just below (of the order of 10 C. below as may be appropriate) the said dew point, whereby such vapours are condensed and separated out of the combustion gases and thefouling. of the turbine blading is prevented or materially reduced. The temperature range covered by the.

fall of temperature in the said separating cham-' ber is chosen to provide a margin on each side of the dew point of the impurity, or in the case of there being two or more impurities with dew points of approximately the same order it ought to cover a range from a little above the dew point of the impurity having the highest dew point to a little below the dew point of the impurity having the lowest dew point so that substantially the whole of the impurity will be deposited in the said chamber and not in the passages leading to or from it.

The cooling of the combustion gasesln the separating chamber may be effected by the ad'- mixture of a cooling agent such as atmospheric air raised to an appropriate pressure, or by contact with cooling surfaces such as pipes through which a cooling agent is passed. The separation of impurities from the combustion gases may be considerably promoted by the presence of certain substances in the combustion chamber which will be referred to for brevity as catalysts although their function may not always be achemical one but have the merely physical effect of forming nuclei of condensation for the impurities. For example a spray of a relatively small quantity of sea water, which is readily available in marine plants, introduced into the separating chamber may promote the deposition of vanadium pentoxide, which is frequently occurring in the combustion gases of certain heavy oils Other objects and features of the invention 1 will become apparent from the following specification wherein, in order that the invention be better understood and readily carried into effect,"

some embodiments thereof will now be described by way of example with reference to the accompanying drawing of which:

l supplies compressed air to the combustion chamber 3 through the cold pass of a heat exchanger 2. Combustion gases from the combustion chamber 3 pass directly into the high pressure gas turbine E which is kept at temperatures T higher than the dew point of the impurity having the highest dew point of all the impurities present in the combustion gases throughout all its stages and at all operative conditions.

The exhaust from turbine 6 is passed through aseparating chamber fi wherein the temperature is. kept at or slightlyv below the dew point of'the impurity having the lowest dew point, and this. is effected by introducing air from the compressor l* directly through a line 1 by-passing the heat exchanger 2,, combustion chamber 3 and high pressure turbine 6.

From the separating chamber 5 the gases flow into the low pressure gas turbine 9. A control valve. la is provided in line 1 as control means to regulate the quantity of cool air supply to the separating chamber and. thus to compensate at least in part for the changed temperature conditions which would otherwise arise in the separating chamber 5 when operating under variable load conditions. Thus, under partial load operation when the temperature of the gases in the separating chamber 5 tendsto fall below the preferred value an increase in the bleed of cool air from thecompressor l to the separating chamber 5 tends to reduce the rate of air flow to the cornbustion chamber 3 and thus, at any given load, to raise the inlet temperature to the high pressure turbine 5 and in consequence to raise the inlet temperature of the gas entering the separating chamber 5. The admission of this. extra.

air to the separating chamber 5 also makes the mass flow-in subsequent turbines, such as the said low pressure turbine 9, bear a greater ratio to the mass-flow through the high pressure turbine 6-; thiscauses the heat drop in the high pressure turbine 6 00 fall in relation to the heat drop in the subsequent turbines suchas the low pressure turbine 9 which tends still further to raise the inlet temperature of the gas entering the 'sepa rating chamber 5.

A catalyst may be present in the separating chamber: 5, preferably in the form of a spray'of sea water introduce'dthrough the pipe 19 into the separating chamber 5, where it may act also as 'a cooling agent.

All onmost-of the impurities which: passed.

in Fig.2, water or. air. cooled contact surfacesmay haust gases'from the low pressure turbine 9 may be brought into heat. exchange in the heat exchanger 2 with the other part of the compressed air supply to. .the' combustion chamber 3 controlled by valve lll if desired.

Although primarily intended for use in connection with gas turbines of the open cycle type developingv useful shaft power, this invention may also be applied to gas turbines of other types includingthose forming. part of chemical, metallurgical or industria'l .process plants, or. those employed to supply 'combhstiorrair under .pressure to the air; boi -l"ers"fo f, closedv cycle gas turbine plants. For the'latterapplication it may be found in some instances, depending'on the cycle temperatures, that the correctpositi'on' for the separating chamber is between. the air boiler of the gas turbine or in between two sections of the air boiler?" What I claim as. my invention and desire to secure by Letters Patent-is:

1. A constant pressure gas, turbine plant comprising a multistage'compresson a combustion chamber, high pressure gas turbine blacling, aseparating chamber, and low pressure gas turbine blading consecutively arranged in the motive'gas stream, a 'by-pass linefroman intermediate stage of said multistage compressor to the said separating chamber, andwalve'meanS in the said by-pass. line adapted to control the flow of by-passed air into. said separating chamber and to adjust the temperaturetherein to a value not exceeding thedewpoint. or vaporous impurities 7 present in the said motive. gas stream.

2. A constant pressure gas. turbine. plant com: prising a multistage compressor, a. combustion chamber, high .pressure gasturbine blading a separating chamber, and low pressuregastur-bine blading consecutively arranged in the motive gas stream, by-passlinef rom'.an intermediate stage of said multistage compressor into the said. separating chamber,. a branch linefrom the high pressure-delivery end of the said compressor to the entrance of thesaidficdmbustbn chamber, a cold heat exchanges pass;arranged through the said separating chainber and connectedin the. said branch line, and valve means-in I the said by-pass lineand in thesaidbranch line arranged for controlling thel flowof air into. and in indirect v heat exchange withthe saidi separating chamber respectively,,andthereby to adjustfthe temperature' therein toa value not exceeding the dew point ofvaporous impurities present in the said motive gases.

' "RoBERrJ MEs ELSH;

REFERENCES" orrEn The-following references. are of record in the.

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